1. Field of the Invention
The present invention relates to a method and a system for setting processing conditions of a laser processing system, such as a laser marker, which performs processing such as printing or marking including characters, symbols and graphics on a work surface with a laser beam, a computer program for setting processing conditions for a laser processing system, a computer-readable recording media or device on which laser processing conditions are recorded.
2. Description of Related Art
A laser processing system scans a given scan field of a subject surface of works (work surfaces) such as components and finished products with a laser beam to apply processing, such as printing and marking of characters, symbols and/or graphics, to the work surfaces. Referring to FIGS. 1 and 2 for the purpose of providing a brief description of a configuration of a laser processing system by way of example, the laser processing system comprises a laser control unit 1, a laser output unit 2 and an input unit 3. Excitation light generated by a laser excitation device 6 of the laser control unit 1 excites a laser media 8 of a laser oscillator 50 of the laser output unit 2. A laser beam L emanating from the laser media 8 is expanded in beam diameter by a beam expander 53 and directed toward a scanning head 9. The scanning head 9 deflects the laser beam L so as to scan a work W in a given scan field, thereby processing, by marking or printing, the work W.
There has been known a laser processing system which is provided with a two dimensional scanning device 9 as shown in FIG. 2. The scanning device 9 comprises a pair of galvanic mirrors that form an X-axis scanner 14a and a Y-axis scanner 14b, and a pair of galvanic motors 51a and 51b to which the galvanic mirrors are mounted for rotation. The X-axis scanner 14a and the Y-axis scanner 14b are arranged so that their axes of rotation perpendicularly intersect with each other and deflect an incoming laser beam so as to scan a scan field in X and Y directions perpendicularly intersecting with each other. The scanning device 9 is provided with focusing means such as an fθ lens system for focusing the laser beam in a given scan field.
There has been known a laser processing system which is provided with a three-dimensional scanning device 14 as shown in FIG. 3. The scanning device 14 comprises a Z-axis scanner comprising a lens system capable of varying its focal length which is referred to as a working distance to a given scan field.
However, since the three-dimensional laser processing system is used for processing three-dimensional works, it is essential to specify a processing pattern such as a character string in three dimensions. A laser processing condition setting program designed to process three-dimensional works requires specifying a processing pattern in three dimensions. On the other hand, three-dimensional works are difficult to be processed in three dimensions according to relative positions between the works and a laser output head of the laser processing system. For example, in the case where it is intended to print a print pattern thoroughly on a top surface of a work W in the shape of a frustum of pyramid on which a rectangular solid WR is put as shown in FIG. 84, when printing the work W with a laser beam L thrown obliquely from above the work W, an area in the shadow of the rectangular solid WR is unexposed to the laser beam and is unprintable consequently. Nevertheless, if going ahead with printing, a print pattern cuts across partly the rectangular solid WR. Even if the laser beam is not cut across by the rectangular solid WR when it is intended to print a print pattern on an inclined side surface of the work W as shown in FIG. 85, an angle of the laser beam L incident upon the side surface may be too small, and, consequently, it is difficult to print a print pattern on the side surface as desired. As shown in an enlarged form, as an incident angle θ of the laser beam L (which is referred to as an angle with a normal line L of the side surface) gets closer to 90°, it becomes difficult to print the side surface with acceptable precision. A critical incident angle or higher limit angle (processing limitation angle) is usually 60°.
Furthermore, a problem encountered by the three-dimensional processing system is that an operative speed of one of three scanners (X, Y and Z scanners) fails to follow up operative speeds of the other two. In an example shown in FIG. 86, since an inclined end surface of the work W has a Z-axis component that is greater than a X-axis component, the Z-axis scanner has a momentum greater than the X-axis scanner. However, since, in general, the Z-axis scanner has a scan speed smaller than the X-axis scanner, the Z-axis scanner is difficult to operate following up the X-axis scanner, so that the laser beam defocuses and, in consequence, forms an elliptical spot in a given scan field. This results in imprecise printing.
As just described above, for various reasons, the three-dimensional laser processing system provides room for an occurrence of a disabling area (in which processing is impossible) and/or a defective processing area (in which processing is possible but defectively) on a work surface. The conventional laser processing system has neither means for detecting of processing defects such as partially chipped print and too light print nor means for detecting a possible occurrence of processing defects. Therefore, the conventional laser processing system relies on the user to ensure that that printing is carried out in a laser beam exposable area and laser beam processable area. Accordingly, if the user has carried out printing without catching on that the settings that the user specified contain a disabling area, the printing causes printing defects such as shear in printing, dull printing, printing in wrong position and the like. Such a printing failure should be avoided in printing of essential indications such as product quality verification, a statement of product liability, a best-before period of food and drinks and the like. Works with printing defects should be disposed. In the case of a laser marking system, since a pattern printing process is often a final stage of a production line, works having printing defects are wasted and are a source of economical loss.
Another problem in avoiding the occurrence of printing defects where the user has to repeat an evaluation as to whether an actually printed pattern is acceptable or not and, if not, he has to adjust settings such as, for example, a printing position. Then, the user tries to print out with the altered settings until a desired result is obtained. This is quite troublesome and a task takes user time and effort.
It is conceivable to use a laser processing condition setting program that confirms, before execution of printing, whether a printing position that the user specified is appropriate or not. An alteration of settings will be performed as described below. After specifying a work and a print pattern, the laser processing condition setting program transfers laser processing data representing the settings to a controller so as thereby to alter a previous content of printing. Subsequently, the controller expands the laser processing data and executes checking on whether a print pattern falls exactly within a printable work surface area for acceptable print. If the print pattern is unprintable, then, the user is informed about the fact by a warning. However, although this approach provides convenient means allowing the user to alter the settings when the settings are improper, it needs to transfer processing data to the controller once and then to expand it. This wastes time in data processing.